Recently, with increasing development of information industries, the general trends in designing information devices (e.g. computer keyboards) are toward small size, light weightiness and slimness. Generally, the keyboard has some specified function keys, for example the Caps lock key, the Number lock, and the like. In addition, plural indicating lamps corresponding to these specified function keys are arranged at other positions of the keyboard or at the hardware component around the keyboard. In a case that one of the specified function keys is pressed, a corresponding specific function is enabled, and thus a corresponding indicating lamp is turned on to result in an identification effect. Since these indicating lamps occupy layout space of the keyboard, the indicating lamps become hindrance from miniaturization of the keyboard. Moreover, too many indicating lamps may confuse the user. Under this circumstance, the user fails to accurately judge which function keys correlate to the illuminated indicating lamps.
For solving the above drawbacks, a keyboard as shown in FIGS. 1 and 2 is disclosed. FIG. 1 is a schematic cross-sectional view illustrating a conventional keyboard. FIG. 2 is a schematic enlarged fragmentary view illustrating the keyboard of FIG. 1. The keyboard 1 comprises a base 11, plural luminous keys 12, plural ordinary keys 13, plural light-emitting elements 14, a membrane circuit board 15 and a plastic film layer 16. The plastic film layer 16 is disposed on the membrane circuit board 15. Each of the luminous keys 12 comprises a keycap 121 and an elastic element 122. Each of the ordinary keys 13 comprises a keycap 131 and an elastic element 132. The keycap 121 of each luminous key 12 has a light-transmissible part 1211. The light-emitting elements 14 are disposed on the membrane circuit board 15 and arranged under the light-transmissible parts 1211 of corresponding luminous keys 12. The luminous keys 12 are specified function keys, which are triggered to enable specified functions. Each of the luminous key 12 further comprises a light shade 123 with an opening 1231. The light shade 123 is made of a rubbery material. In addition, the corresponding light-emitting element 14 is enclosed by the light shade 123. Consequently, the light beam emitted by the light-emitting element 14 is only permitted to be transmitted through the opening 1231 of the light shade 123 without being scattered to the periphery of the light shade 123.
Moreover, the membrane circuit board 15 comprises an upper circuit board 151, a lower circuit board 153 and a partition plate 152. The partition plate 152 is arranged between the upper circuit board 151 and the lower circuit board 153. Corresponding to the plural keycaps 121 and 131, plural upper contacts 1511 and plural lower contacts 1531 are respectively formed on the upper circuit board 151 and the lower circuit board 153. Corresponding to the plural upper contacts 1511 and the plural lower contacts 1531, plural perforations 1521 are formed in the partition plate 152. The upper contacts 1511, the lower contacts 1531 and the perforation 1521 that are aligned with each other collectively define a membrane switch 154. When one of the keycap 121 or 131 of the key 12 or 13 is pressed, the keycap 121 or 131 is moved downwardly to compress the elastic element 122 or 132, so that the elastic element 122 or 132 pushes against the corresponding upper contact 1511. Consequently, the upper contact 1511 is contacted with the corresponding lower contact 1531 through the corresponding perforation 1521. When the upper contact 1511 and the lower contact 1531 are contacted with each other, the corresponding membrane switch 154 is electrically conducted, and thus a corresponding key signal is outputted from the keyboard 1. On the other hand, when the pressing force exerted on the keycap 121 or 131 is eliminated, an elastic force provided by the elastic element 122 or 132 is acted on the keycap 121 or 131, so that the keycap 121 or 131 is moved upwardly and returned to an original position.
In addition, when the keycap 121 of one of the luminous keys 12 is pressed and the specified function is enabled, a corresponding light-emitting element 14 is driven to emit a light beam in response to the key signal. The light beam will be transmitted to the surroundings through the opening 1231 of the light shade 123 and the light-transmissible part 1211 of the keycap 121. Since the light shade 123 has a function of converging the light beam, the intensity of the light beam emerged from the light-transmissible part 1211 of the keycap 121 is increased to facilitate the user to realize whether the specified function corresponding to the pressed luminous key 12 is enabled.
Since the light shades 123 of the luminous keys 12 are attached on the plastic film layer 16 by adhesion, some drawbacks of the keyboard 12 occur. For example, during the process of attaching the light shade 123 on the plastic film layer 16, if the light shade 123 is suffered from misalignment, the corresponding light-emitting element 14 fails to be completely enclosed by the light shade 123. Under this circumstance, after the keyboard 1 is produced, the intensity of the light beam emerged from the light-transmissible part 1211 of the keycap 121 is usually insufficient. In addition, if the adhesion between the light shade 123 and the plastic film layer 16 is poor, the light shade 123 is easily detached from the keyboard 1. Once the light shade 123 is detached, the light beam emitted by the light-emitting element 14 will be scattered everywhere because the light-emitting element 14 is no longer enclosed by the light shade 123. Under this circumstance, the intensity of the light beam emerged from the light-transmissible part 1211 of the keycap 121 is considerably insufficient.
Moreover, since the light shade 123 is made of a rubbery material, the thickness of the light shade 123 is at least d1 according to the current technology of processing the rubbery material. The distance between the bottom surface of the keycap 121 and the top surface of the light shade 123 is d2. When the keycap 121 of the luminous key 12 is pressed and the keycap 121 is moved downwardly for the distance d2, the bottom surface of the keycap 121 will be contacted with the top surface of the light shade 123. Under this circumstance, the light shade 123 becomes hindrance from continuously pressing the keycap 121. For making electrical conduction of the membrane switch 154, the pressing force acting on the keycap 121 should be increased to move the light shade 123 and the elastic element 122 downwardly. In other words, during the process of pressing the keycap 121, the movement of the keycap 121 is interfered by the light shade 123. Under this circumstance, the finger's tactile feel is unsatisfied.